Peroxides have, as a general property, a tendency to be flammable and explosive with some peroxides exhibiting such properties to a greater extent than others. For example, benzoyl peroxide may decompose when dry due to shock, friction, or static electricity. This property carries with it the hazards to the users of these materials as well as to the manufacturers and intermediate handlers thereof. Accordingly, it has long been an object to provide flame resistant organic peroxide compositions.
The safety and end-use advantage provided by water-soluble or water-dispersible peroxides has been recognized. However, many peroxides of commercial interest are water insoluble. Moreover, dispersions containing relatively high concentrations of water insoluble, solid peroxides are typically quite viscous and therefore difficult to handle and process. This problem is particularly aggravated as the particle size of the peroxide is reduced. For example, when milling a peroxide in water to reduce its particle size below 10 μm, the aqueous dispersion often forms a very thick paste. Further milling becomes quite difficult unless milling is discontinued for a period of time to permit the dispersion to “relax” and soften to an extent where milling again becomes feasible. These difficulties significantly lengthen the period of time necessary to achieve a desired small particle size. As there are many end use applications for water insoluble peroxides where smaller particle size will be advantageous, there remains a need for highly concentrated aqueous dispersions of small particle size peroxides which are capable of being handled by pumping and/or pouring as well as methods by which such aqueous dispersions may be conveniently and efficiently prepared.
Water-insoluble, solid organic peroxides such as benzoyl peroxide are widely used as bleaching agents, for example in the decolorization of food products such as flour, whey and cheese. See Yehia El-Samragy, “Benzoyl Peroxide—Chemical and Technical Assessment (CTA),” 61 JECFA, 2004.